Fleece Yield & Yarn Calculator: How Much Yarn Will Your Fleece Produce?

A raw fleece straight off the sheep contains lanolin, vegetable matter, and general dirt that can account for 25–50% of its total weight. Once scoured (washed), the clean yield is significantly less than what you started with. After spinning, the yardage of yarn you get from a given weight of clean fleece depends on the twist, thickness, and spinning technique. The Fleece Yield & Yarn Calculator helps spinners, weavers, and craft producers understand what to expect from their fleece.

Breed type selection covers common UK breeds from fine Merino and Bluefaced Leicester through to coarser breeds like Herdwick and Swaledale, each with a characteristic clean yield percentage. The calculator returns estimated clean fleece weight after scouring and estimated spun yarn yardage for three yarn weights: lace, sport, and worsted/aran.

A vegetable matter (VM) adjustment allows for fleeces with higher than average contamination from hay, twigs, or short fibres (second cuts).

Clean yield percentages are derived from the British Wool Marketing Board breed data and AHDB Sheep fleece grading guides. Yarn yardage estimates are based on the standard grist calculations used in commercial spinning, with adjustments for hand-spinning efficiency (typically 70–80% of commercial spinning yardage for a comparable yarn weight).

Enter the raw weight of your fleece in kilograms or grams. Select the breed type from the list. Adjust for vegetable matter if the fleece is particularly dirty or contains a lot of short fibres. The calculator returns your expected clean yield after scouring and the estimated yardage for three yarn weights. Use these figures when purchasing fleeces to ensure you are buying enough for your project.